1. Field of the Invention
The present invention concerns the preparation of nanoparticle formulations containing hydrophobic or hydrophilic photosensitizers and their use in photodynamic therapy, particularly for tumor and antibacterial therapy, using intravenous or topical administration.
2. Invention Disclosure Statement
Calcium phosphate nanoparticles have gained increasing interest in recent years due to their high biocompatibility which is due to the fact that calcium phosphate constitutes the inorganic mineral of mammalian bone and teeth (S. V. Dorozhkin, M. Epple, Angew. Chem., Int. Ed., 2002, 41, 3130-3146; M. Vallet-Regi, Dalton Trans., 2006, 5211-5220; C. Rey, C. Combes, C. Drouet, H. Sfihi, A. Barroug, Mater. Sci. Eng., C, 2007, 27, 198-5220). Calcium phosphate nanoparticles can also act as drug carriers, e.g. for nucleic acids (V. Sokolova, M. Epple, Angew. Chem. Int. Ed., 2008, 47, 1382-1395) or for antitumor drugs (B. Palazzo. M. Iafisco, M. Laforgia, N. Margiotta, G. Natile, C. L. Bianchi, D. Walsh, S. Mann, N. Roveri, Adv. Funct. Mater., 2007, 17, 2180-2188; E. Boanini, M. Gazzano, K. Rubini, A. Bigi, Adv. Mater., 2007, 19, 2499-2502; X. Cheng, L. Kuhn, Int. J. Nanomed. 2007, 2, 667-674). For instance, a successful cell transfection was achieved with DNA- and siRNA-coated calcium phosphate nanoparticles (A. Maitra, Exp. Rev. Mol, Diagn., 2005, 5, 893-905; Y. Kakizawa, S. Furukawa, A. Ishii, K. Kataoka, J. Controlled Release, 2006, 111, 368-370; V. V. Sokolova, I. Radtke, R. Heumann, M. Epple, Biomaterials, 2006, 27, 3147-3153; D. Olton, J. Li, M. E. Wilson, T. Rogers, J. Close, L. Huang, N. P. Kumta, C. Sfeir, Biomaterials, 2007, 28, 1267-1279; V. Sokolova, A. Kovtun, O. Prymak, W. Meyer-Zaika, E. A. Kubareva, E. A. Romanova, T. S. Oretskaya, R. Heumann, M. Epple, J. Mater. Chem., 2007, 17, 721-727). Another example is disclosed in the Patent No US 2008/0241256 A1 by Kuhn. Here calcium phosphate nanoparticle active agent conjugates suitable for targeting active agent delivery to tumor cells and lymphatics for the treatment of cancer and the treatment or prevention of cancer metastasis are described. Even though the enhanced drug delivery system may provide many advantages over prior art formulations, the anticancer drugs adsorbed onto calcium phosphate nanoparticles are either chemotherapeutic or releasing hormone agonists which may have numerous serious side effects, because they interfere with normal cell growth as well as cancer cell growth.
Inorganic nanoparticles exhibit various advantages towards organic nanoparticles: They are not attacked by microbial strains, they are frequently non-toxic, the preparation is easy and the storage stability is commonly good. (V. Sokolova, M. Epple, Angew. Chem., Int. Ed., 2008, 47, 1382-1395). Especially calcium phosphate nanoparticles fulfill all these advantages, because they are both biodegradable and biocompatible (D. Tadic, F. Beckmann, K. Schwarz, M. Epple, Biomaterials 2004, 47, 3335-3340; C. Schiller, M. Epple, Biomaterials 2003, 24, 2037-2043: D. Tadic, F. Peters, M. Epple, Biomaterials 2002, 23, 2553-2559; S. V. Dorozhkin, M. Epple, Angew. Chem. Int. Ed. 2002, 41, 3130-3146). In addition, they are structurally and chemically very close to the mineral in human bone (S. Weiner, H. D. Wagner, Annu. Rev. Mater. Sci. 1998, 28, 271-298). Another benefit of calcium phosphate nanoparticles is the possibility to incorporate lanthanides. These lanthanide-doped particles show fluorescence therefore it is easily possible to track the pathway through e.g. cells. (A. Doat, M. Fanjul, F. Pelle, E. Hollande, A. Lebugle, Biomaterials 2003, 24, 3365-3371; A. Doat, F. Pelle, N. Gardant, A. Lebugle, J. Solid State Chem. 2004, 177, 1179-1187; A. Lebugle, F. Pelle, C. Charvillat, I. Rousselot, J. Y. Chane-Ching, Chem. Commun. 2006, 606-608; S. Padilla Mondejar, A. Kovtun, M. Epple, J. Mater. Chem. 2007, 17, 4153-4159; V. Sokolova, A. Kovtun, R. Heumann, M. Epple, J. Biol. Inorg. Chem. 2007, 12, 174-179).
Photodynamic therapy (PDT) is a promising technique being explored for use in a variety of medical applications and is known as a well-recognized treatment for the destruction of tumors (T. D. Mody, J. Porphyrins Phthalocyanines, 2000, 4, 362-367). Photodynamic therapy uses light and a photosensitizer (a dye) to achieve its desired medical effect. A large number of naturally occurring and synthetic dyes have been evaluated as potential photosensitizers for photodynamic therapy. Perhaps the most widely studied class of photosensitizers are the tetrapyrrolic macrocyclic compounds. Among them, especially porphyrins and chlorins have been tested for their PDT efficacy.
Nevertheless, many photosensitizer formulations do not have chemical, pharmacological and/or photo-physical properties to improve the bioavailability and hence the effectiveness of the photosensitizer to achieve an effective PDT treatment.
Thus, many attempts have been made to improve the photosensitizer bioavailability by altering its pharmacokinetic and biodistribution. Providing organic nanoparticles as drug carriers, Patent No US 2004/0047913 A1 by Allemann et al. discloses nanoparticle photosensitizers comprising green porphyrins and nanoparticles selected from polyester polymers such as poly(D,L-lactide-co-glycolide) and poly(D,L-lactide). Nevertheless, as previously mentioned organic nanoparticles have shown to exhibit various disadvantages compared to inorganic nanoparticles. Moreover, biodegradable polymer-based drug delivery carriers can often form polymer acidic byproducts or degrade into fragments that may modify the environment where the active agent is being release and may adversely affect the drug and/or the tissue they interact with.
Another photosensitizer formulation comprising luminescent nanoparticles with attached photosensitizers for PDT applications is disclosed in Patent No US 2007/0218049 A1 by Chen et al. Upon exposure to ionizing radiation emitted by X-rays, alpha particles, beta particles, neutrons and gamma rays, luminescent nanoparticles emit light to activate the photosensitizers, which in turn produce a PDT killing effect in cancer cells. As luminescent nanoparticles need to be exposed to an ionizing radiation source the important advantage of high selectivity to killing tumor cells with minimal damage to surrounding tissue in PDT is lost. Even though, the killing effect in cancer cells is amplified by activation of the photosensitizer, healthy tissue such as skin or organs which ionizing radiation must pass through in order to treat the tumor is subjected to the hazardous effect of ionizing radiation.
Most substances successfully employed for photodynamic tumor therapy are lipophilic substances, which due to their inherent low solubility in water need to be formulated in a proper way to enhance their uptake and bioavailability. Highly hydrophilic substances on the other hand cannot be used for photodynamic tumor therapy as they do not sufficiently accumulate in the tumor tissue.
Another possible application of PDT is the treatment of infectious diseases caused by pathogenic microorganisms (M. Wainwright, Photodiagn. Photodyn. Ther., 2005, 2, 263-272). A constant problem in the treatment of infectious diseases is the lack of specificity of the agents used for the treatment of these diseases. Secondly, microorganisms can adapt and thus negate the effect of most chemically designed antimicrobials creating resistant strains, which require ever more active ingredients to stop their activity. In this respect PDT has been identified as a promising alternative as due to its different mode of action. In addition, there is only a very low possibility for the formation of resistant bacterial strains.
The use of PDT for the treatment of various types of disease has been limited due to the inherent features of photosensitizers (PS). These have included their high cost, extended retention in the host organism, substantial skin photo toxicity, low solubility in physiological solutions (which also reduces its usefulness for intravascular administration as it can provoke thromboembolic accidents), and low targeting effectiveness. These disadvantages, particularly of PS in the prior art, had led to the administration of very high doses of a photosensitizer, which dramatically increase the possibility of accumulation of the photosensitizer in non-damaged tissues and the accompanying risk of affecting non-damaged sites.
Efforts to reduce cost and to decrease background toxicity have been underway but are unrelated to the developments of the present invention. Work to improve solubility in physiological solutions, effects of skin photo toxicity, retention in host organism and to a lesser extent targeting effectiveness are the areas where the present invention provides new and non-obvious improvements on the use of PDT to treat various hyperplasia and related diseases as well as bacterial infections. Moreover, since the application of photodynamic therapy in the treatment of cancer and other diseases is increasing rapidly, there is also a bigger demand for new photosensitizer formulations. These new photosensitizer formulations need to be stable, easy to manufacture and to handle.